hands definitely. That way you can feel your partner's body and how they are reacting to your touch. I's usually more awkward to use something else to massage with and in my opinion it is just a lot more intimate using your hands

This reminds me of Ross on Friends when a girl rings the bell and she's supposed to bring her dad to Phoebe but she isn't available. Ross thinks he can massage the hot girl then she sends the old man in and Ross massages him with wooden spoons!

I wouldn't use any tool for a massage, just the hands and fingers, that's the sexiest to feel the touch of the other person either giving or receiving.